Mouse-human somatic cell hybrids containing either human chromosome 6, or 7, or 16, or 17, or 17 carrying the region p21 yields pter of human chromosome 6 as the only human chromosome present in the hybrids have been already produced and injected into syngeneic mice. Sera from hyperimmunized mice will be used to characterize the surface antigens coded by these human chromosomes and to further localize the position of the genes coding for these antigens on the respective human chromosomes. We will also determine whether the cellular immunoresponse to human histocompatibility antigens expressed in hybrid cells containing human chromosome 6 or part of human chromosome 6 is H2 restricted. The expression of H2 and HLA antigens will also be studied in hybrids between F9 mouse teratocarcinoma cells and either mouse cells derived from different mouse strains or human cells to determine whether in the undifferentiated hybrid cells the expression of H2 and HLA antigens is shut off and whether concordant expressions of mouse and human histocompatibility antigens occur in the differentiated hybrid cells. Syngeneic mice will also be hyperimmunized with somatic cell hybrids containing either chromosome 6 or the region p21 yields pter of human chromosome 6 and expressing HLA 3 and 7 or HLA 32, and their spleen cells will be fused with P3x63Ag8 mouse myeloma cells to obtain hybrids which produce antibodies againt human histocompatibility antigens. This study should result in the selection of a series of hybrid clones producing monoclonal antibodies to different human histocompatibility antigens. In addition, we intend to study the cellular and humoral immunoresponse to Epstein-Barr (EB) virus nuclear antigen (EBNA) and surface antigens using somatic cell hybrids between mouse cells and Burkitt's lymphoma cells.